Center



*March l 1949- sfAuHoLloHANj-l 2,463,385 V CENTER 4 V .Filed Sept. 11 1945 Patented Mar. 1, 1949 UNITED STATES PATENT 0F FICE 3. Claims. (Cl. 82H33.)

This4 invention generallyV relates to centers for. supporting; workpieces to.` be machined, and more specincally to a novel structure particularly adapted to function as; a dead center for use in grinding machines;v and thev like, though being; capable of: generaluse` both. as a dead and asv a live center in various kinds of machines.

A` device according to the; invention belongs to that. categoryV ot centers that com-prise a flat,- end face. formed.. i-n an element. ofA the structure in az plane perpendicular to the longitudinal axis. of the. center... adapted to be engaged. by the: end. of the. workpieca and a spring pressed, center pin projecting through.; said flat tace and adapted to be received. within the center hole oi the end of the workpiece-` and longitudinally displaceable re1- ative. to the body` oi the. center, tol permit engagement of the flat face aforesaid by the workpiece irrespective of variations in the depth of the center hole.

The. general object` of the invention is to Iprovide anovel and improved center of the character described adapted to be mounted in a supporting member in the. manner of a. conventional center, which. is of sturdy and relatively simple construction. precise. in operation,t readily 'assembled and disassembled to. permit substitution of parts whenever required, and capable of entirelysatis-i. factory use with workplaces of considerably dif.- ferentsizes.

Another obj-ect. is to provide. a center wherein the, flatv tace engageable by the workpiece is formed on an elementy of the structure mounted tor rotation relative to the body of the center and independent. oi the,Y center pin,l said element beingl changeable to provide different areas of. contact. for the workpiece.

A further object is to provide adjustable means :amlapted to prevent` inward displacement or the center pin after theV workpiece has been brought Lf into contactwith the flatrsurface aforesaid,v so as to lock the center pin in engagement with the work. The invention also contemplates the pro.v vision ot further adjustable means for limiting the outward. movement` of the center Din.

Still another object is to provide means for varying the. pressure exerted by the spring. means acting'. ony the` center pin, so as. to insure proper support for the. workpiece without. objectionable. friction. between associated surfaces. These and'. other related objects will become` apparent in the iollowingf description of the. invention illustrated! iny the. drawings., wherein:

Figi.. l. is a. vertical longitudinal section through ai center accordineto the invention, showing. the

structure and the-arrangement of the various ele.- mentsthereoi.

Eiga. 21 is a similar vertical longitudinal sect1-ion through. the Center, showing elements of the structure adj-usted' to a different position.

Fig. 3;v is a. fragmentary longitudinal sectional view ofy the center on line 3-.-3 of Fig.. 4. illus. trating; an modied embodiment of the, invention.

Fig. il" is av cross.- sectiei'ialv view on, line. lle-A` oi Eliane. v

Referring new in. detail to the drawings, lilinf dicatesthe body` 0i the center which. is provided with an externally tapered portion adapted-to. t. conventional center supporting devicesyv and with an; axial borev I'I extending from end. to end ofthe body'.

The forward end` of the center body is provided with a ball bearing I2 which i-s retained in Dosis tion by means of a lock ring i3 mounted on a suit. ably threaded portion of the outer surface of the body. An annular element HIA having a center opening I-5 for the center pin i6. is. secured to the. ball bearing by means of a plurality of small screwsv lli. The element I44 is. formed with a front flat face t8 in a. plane perpendicular tor the. axis, of thel body lll, which face intended to beengag-ed: by the4 end oi the workpiece The element` Ut may have. openings l5 of. different diameter so as to denne surfaces. i8 engageable even by workpieces of small diameter, in which case vof course the center pin i6. will project. from the element I4 by a reduced amount. As hereafter described,` means. are provided for limiting the ontward displacement of the. center pin and thereby preventing this.. latter from. bearing' Aagainst andexerti-.ne an obiectionabIe thrust 0n. the clement. 1,4.

A cylindrical member l 9. is mounted within theI bore il.,J the. outer surface of this member as well; as 4` the. inner surface` of the body Il) being accuratelv machined to insure, av close sliding nt. The forward end oi the member i9 has threaded therein the shank of the. center pin, I`6,. the, conical portionwhereof is. adapted to engage .the usual center hole drilled in the workpiece. The periphery of; member la is provided with a triangular cutto define. anincli'ned' surface 2D engageable by a. screw 2L, threaded through the body lll' and adjustable. to. limit the inward displacernentv of the member t9' and therefore l0f the center pin Carried.. thereby. A longitudinal.' slot. Z2. is likewise4 provided at. ther peripheryl of the member la, and' the, screw Zithreaded in the body' t0 'projects into; said slot to prevent the rotation of the member Iain the. operation of the device'` The member I9 is formed at its rear end with an extension 24 of reduced diameter, dening a shoulder 25 and embodying a threaded axial bore 26 for the purpose that will become hereafter apparent.

A closure member 21 is mounted in the bore I I at the rear end of the body IU, and is removably secured thereto by a plurality of small screws 23 passing through a flange portion of the member juxtaposed to the body end. The member 21 is provided with a threaded axial bore 29 for receiving an externally threaded longitudinally adjustable sleeve 30, which extends into the bore I I to a point spaced from the extension 24 and is formed with a iiange 32 within said bore.

A coil spring 33 is mounted on the extension 24 and the inner end portion of the sleeve 36, and bears against the aforementioned shoulder 25 and flange 32 so as to urge the slidable member I9 outwardly in the direction of the element I4 and thereby press the center pin into engagement with the surfaces of the center hole of a workpiece contacting the face I8 of the element I4 in the operation of the device. By virtue of the longitudinal adjustment of the sleeve 30, the pressure exerted by the spring 33 may be varied to maintain the thrust exerted by the center pin I1 on the workpiece within the limits required for va firm engagement yet avoiding excessive friction with the surfaces of the center hole. The sleeve 30 is locked in any desired adjusted position by a lock nut 34 abutting against the rear face of the member 21.

The sleeve 30 is also longitudinally bored to receive for longitudinal movement therein an eX- ternally threaded rod 36 which is fastened within the bore 26 of the aforementioned extension 24. Said rod 36 extends rearwardly beyond the lock nut 34 and carries at its rear end a knurled nut 31 which may be turned in one direction to displace the rod rearwardly and thereby move inwardly, in opposition to the spring 33, the member I9 rigidly connected therewith, to withdraw the center pin from the annular element I4. By rotating the nut 31 in the opposite direction, the spring 33v will of course move again the member I9 outwardly. A nut 38 is provided for locking the rod 36 and associated elements in any adjusted position. By means of this arrangement the outward movement of the member I9 carrying the center pin may be therefore variably limited.

In operation, the previously faced end of the workpiece is brought into contact with the at outer face I8 of the annular element I4 secured to the ball bearing I2 (which latter functions as a thrust bearing) and is free to rotate relative to the stationary center pin I6. In the movement of the workpiece toward the element I4, the conical portion of the center pin is engaged by the surfaces of the center hole of the workpiece and displaced thereby inwardly together with the member I9, in opposition to the spring 33, until the end of the workpiece comes into contact with the element I4. The amount of inward displacement depends upon the adjustment of the means for limiting the outward movement of the member I9 hereinbefore described. The screw 2| which had been previously partially withdrawn from the bore II, is then tightened to engage the inclined surface 29 of the member I 9, thereby preventing further inward displacement of this latter member and locking the center pin within the center hole of the workpiece in supporting engagement therewith regardless of any axial thrust that might develop in the cutting operation and cause, in the absence of a locking device, disengagement or partial Withdrawal of the pin from the center hole.

Figs. 3 and 4 illustrate a modified embodiment of the means for limiting the inward displacement of the member I9. In this embodiment, a pin 40 is substituted for the screw 2| and is freely mounted in a radial opening of the body I6 to rest on the inclined surface of the member I 9, the outer end of said pin protruding from the body being received within an eccentric internal groove 4I of a ring 42 which is rotatably mounted on the body. The ring has an opening, at the deepest point of the groove, which may be brought into registration with the aforesaid radial opening in the body, to permit insertion of the pin 40 into this latter opening and then is closed by a removable plug 43. A further threaded opening is provided in the ring, at the shallowest portion of the groove, to receive a set screw 44 projecting into a groove 45 at the periphery of the body I0, said screw guiding the ring in its rotation and cooperating with the pin 40 to prevent lateral displacement of the ring. By rotating the ring 42, the bottom surface of the eccentric groove 4I is caused to exert a camming action on the pin 40 to lock the same in engagement with the inclined surface 20 of the member 29, thereby preventing inward displacement of this latter member.

While I have described my invention substantially with reference to a preferred embodiment thereof, it is to be understood that many changes and modications may be made in the structures illustrated in the drawings without departing from the spirit of the invention or exceeding the' scope of the claims.

I claim:

1. A center comprising a body, an axial bore extending throughout the length of said body, an annular element rotatably mounted at the forward end of said body and having a flat face, in a plane perpendicular to the axis of the body, engageable by a workpiece, a member slidably mounted in said bore and carrying a center pin adapted to project through said annular element, said slidable member having a shoulder, a member for closing the rear end of the body, a sleeve mounted in said closure member and extending into the body, a flange in said sleeve within the body, a spring mounted between said shoulder of the slidable member and said flange of the sleeve to urge the slidable member outwardly and the center pin into engagement with the workpiece, said sleeve being longitudinally adjustable to vary the pressure exerted by the spring, means fuariably limiting the outward movement'of the slidable member and means for limiting the inward movement of the slidable member.

2. A center comprising a body, an axial bore extending throughout the length of said body, a ball bearing mounted at the forward end of said body, an annular element secured to said ball bearing for rotation therewith and having a at face, in a plane perpendicular to the axis of the body, engageable by a workpiece, a member slidably mounted in said bore and carrying a center pin adapted to project through said annular element,V said slidable member having a shoulder at its rear end, a member for closing the rear end of the body, a sleeve mounted in said closure member and extending into the body, a flange on said sleeve within the body, a spring mounted between said shoulder of the slidable member and said ange of the sleeve to urge the slidable member outwardly and the center pin into engagement with the workpiece, said sleeve being longitudinally adjustable to vary the pressure exerted by the spring, means for locking said sleeve in adjusted position, means for variably limiting the outward movement of the slidable member and means for variably limiting the inward movement of the slidable member.

3. A center comprising a body, an axial bore extending throughout the length of said body, a ball bearing mounted at the forward end of said body, an annular element secured to said ball bearing for rotation therewith and having a flat face, in a plane perpendicular to the axis of the body, engageable by a workpiece, a member slidably mounted in said bore and carrying a center pin adapted to project through said annular element, said member having an extension of reduced diameter defining a shoulder, a member for closing the rear end of body, a sleeve mounted in said closure member and extending into the body, a ange on said sleeve Within the body, a spring mounted between said shoulder of the slidable member and said ange of the sleeve to urge the slidable member outwardly and the center pin into engagement with the workpiece, said sleeve being longitudinally adjustable to vary the pressure exerted by the spring, a rod in the sleeve fastened to said extension of the slidable member and projecting rearwardly of the body, means adjustable on said rod externally of the body to variably limit the outward movement of the rod and therefore of the slidable member, and means for variably limiting the inward movement of the slidable member.

BARTHOLOM'EW A. HOLOHAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date l190,918 McKenna Jan. 31, 1893 979,034 Rowe Dec. 20, 1910 1,912,987 Lovely June 6, 1933 FOREIGN PATENTS Number Country Date 558,312 France Aug. 25, 1923 

